Rather, the "anomalies" that Data proposed tracking is the dispersion of space when a ship warps in. The ship takes the place of whatever was in its arrival destination, causing detectable ripples. Kind of like jumping in a pool, you're going to make a splash. Also, it is going to leave a vacuum in the place you just left, so space gases and particles will fill that void.

Contrary to popular belief, space isn't a total vacuum. There's stuff up there.

Metryq wrote:

"Gaseous anomalies"? I immediately think ST6 when I hear that bit of techno-babble. The movie begins with Starfleet's latest and finest "boldly going" out to do grunt work—mapping gaseous anomalies.

TNG's The Battle came out in 1987, a full four years before Star Trek VI.